Ketone body that cannot be detected by Rothera's test:

Rothera's test can only detect acetoacetate and acetone, and not beta-hydroxy butyrate. Rothera's test: Ketone bodies react with sodium nitroprusside (in the presence of NH3) to form a purple colored ring. Positive test indicate Acetoacetate and Acetone. No specific test available for beta-hydroxy butyrate. So, it is first oxidised to Acetoacetate, then Rothera's test is performed.